Subaru WRX Forum banner

Fine knock learn numbers

45K views 6 replies 2 participants last post by  Cujoman10 
#1 ·
So I did a 3rd gear pull in my 2013 wrx, and I'm still learning how to read the values. I didn't get any feed back knock, but I can see I got some fine knock learn. I read through cobbs thing for how to read the numbers, but still a little fuzzy on whats good, and whats not. So I'm going to post it here for the more knowledgeable people to take a look at it. Thanks in advanced!
 

Attachments

#2 ·
Generally speaking, fine learning knock is a way for your ECU to put in a timing compensation (by reducing timing advance, in your case by -1.4 degrees) for a specific area of the map after repeated knock events have happened in that area of the map.

Under a quality tune, you should therefore NEVER have any Fine Learning Knock Correction. If you do experience it, it's likely because you have too much timing, or your AFR is off and you're running a bit too lean. In your case it looks like this happens as your turbo is spooling.

Some people say it's ok, and do run small Fine Learning Knock correction numbers. Personally, it's easy enough for me to tune to fix them so my motor runs as healthy as possible while making clean power.

Think of it this way, it's better to make a little less power by turning down timing in that area of the map .25-.5 a degree where knock happens... rather than the ECU placing -1.4 correction for the whole area of the map.... OR worse, if you are running aggressive timing all around, if you get Feedback Knock Correction of say -2.8 or -4.2 in random areas of the map... that's a LOT of power lost due to a correction that can be prevented from happening in the first place.

Try this:
-Look at learning table values to see exactly what part of the map the Fine Learning Knock correction is happening at (although you can determine that by looking at RPM and load where the Fine Learning Knock Correction kicks in, and at which point it stops)
-Reset your ECU
-Use your AP to lower global ignition timing by 1 degree
-Drive around normally until your IAM (or in your case DAM) stabilizes to whatver the number it should be
-Do some pulls to see if you Fine Learning Knock comes back

note on this: I believe the global ignition timing correction is ONLY applied until the car is turned off, so it's merely a tuning tool to allow you to check your timing. So all this will tell you is that you should probably run a little less timing. Or, if the knock comes back, perhaps you're running too lean during spool up and should add just a little bit more fuel, OR perhaps your turbo is spooling faster than the map that was designed for so both timing and fuel could be off since you're producing more boost in that area of the map than the map expects.

Another side note, when you do your pulls to log, start at a lower RPM (go WOT before the turbo starts to spool, such as 2000rpm). This will allow your turbo to spool naturally, rather than slingshot when you go WOT.

Good luck, keep asking questions! :)
 
#4 ·
Yeah I got my car pro tuned a couple months back. I know very little about tuning cars, and still learning what I'm exactly looking at when I do logs. I send data logs over to the shop I went to, and he says it looks good to him. I've heard mixed things also on fine knock learn. About what's acceptable, and what not. But I know you don't usually wanna see either knocking or it pulling timing to prevent knock.


Sent from my iPhone using Tapatalk
 
#6 ·
It depends on which type of Knock Correction your ECU is applying.

You're right, Feedback Knock can happen, it happens on stock motor, even higher numbers for various reasons from imperfections in gas, to elevation changes, whatever.

I've seen Feedback Knock numbers above 5 before and unless that's happening very regularly I would not worry about them. On my car I geat -1.4 Feedback Knock lets say every 10-45 miles of highway driving varying conditions, and a bit more frequently when driving on street. It goes up quite a bit when conditions vary a lot (pulls, changing gears, engaging Anti-Lag for example) so on.

Fine Learning knock on the other hand is different. Personally, I prefer to NEVER see any on a map that I drive daily. That's just me, I blew one motor already, I'd prefer not to do another ;)
 
#7 ·
That's what I don't want to happen lol. This is my first car that I ever got tuned, and dove head first into all this. Yeah I noticed the knock, and knock learn isn't consistent. Happens under different variables all the time. But I will notice either knock or knock learn when I do WOT pulls. I've never seen that stay 0 on either side since I learned what to start looking for


Sent from my iPhone using Tapatalk
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top